A consumable supply such as a toner cartridge is mounted in an image forming device so as to be replaced by a user as a replaceable unit. Specifically, when the toner cartridge reaches the end of its usefulness as the replaceable unit (for example, when the level of toner contained in the toner cartridge is equal to or below a predetermined level), the user takes the toner cartridge out of a main casing of the image forming device, and then mounts a new toner cartridge in the main casing.
There is known an image forming device which determines whether or not a replaceable unit is a genuine product with respect to the image forming device, provided that the replaceable unit has been mounted in the main casing. Japanese Patent Application Publication No. 2005-326731 discloses an image forming device which includes a memory chip in a main casing. In this configuration, the memory chip can wireless-communicate with a replaceable unit. The contents stored in the memory chip are read by a wireless communication unit provided in the main casing via wireless communication. Based on the readout contents, the image forming device determines whether or not the replaceable unit mounted in the main casing is a genuine product.